Top Gear host Chris Evans has controversially stepped down from his role after only six episodes, in yet another setback for the rebooted series.

Evans announced his departure on social media overnight.

"Stepping down from Top Gear," he wrote.

"Gave it my best shot but sometimes that's not enough. The team are beyond brilliant, I wish them all the best."

The show's 23rd season launched in May, with Evans heading a new guard set with replacing perennial favourites Jeremy Clarkson, James May and Richard Hammond. Evans was charged with the difficult assignment of succeeding Clarkson, who was suspended in March, 2015, and later sacked, after a string of scandals that plagued the show.

The opening episodes of 2016 yielded mixed success. Ratings have been in freefall since the opening night, when 6.42 million UK viewers tuned in, dipping to as low as 1.9 million for the sixth and final episode.

In a statement issued via the BBC, Evans said he would remain a huge fan of the show. He said he stood aside because he believes it's the "best thing I can do to help the cause".

How Evans' departure affects the show's other hosts remains unclear. A major criticism of Evans was that he tried too hard to channel Clarkson in his presenting role. One encouraging sign for the show has been the rise of motoring journalists Chris Harris and Rory Reid, who have both struck a chord with viewers on Top Gear and its sister service, Extra Gear.